WATCHES: Severe Thunderstorm Watch Number 554

WWUS20 KWNS 061933
SEL4
SPC WW 061933
IDZ000-MTZ000-WYZ000-070300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 554
NWS STORM PREDICTION CENTER NORMAN OK
135 PM MDT MON JUL 6 2009

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

EASTERN IDAHO
PARTS OF SOUTHWEST AND CENTRAL MONTANA
NORTHWEST WYOMING

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 135 PM UNTIL 900
PM MDT.

HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 185
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 25 MILES SOUTH OF
DRUMMOND MONTANA TO 55 MILES EAST OF HARLOWTON MONTANA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU4).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

OTHER WATCH INFORMATION...CONTINUE...WW 553...

DISCUSSION...A POTENT AND WELL-DEFINED SHORT WAVE TROUGH AND
ASSOCIATED COLD FRONT WILL MOVE ACROSS THE ROCKIES AND ENCOUNTER AN
INCREASINGLY UNSTABLE AIRMASS ALONG AND EAST OF THE CONTINENTAL
DIVIDE THIS AFTERNOON. AS THE SYNOPTIC FORCING ACTS TO STEEPEN MID
LAPSE RATES...BOUNDARY LAYER MOISTENING/WARMING WILL CONTRIBUTE TO
MLCAPE IN THE 800-1200 J/KG RANGE...MORE THAN ADEQUATE TO SUPPORT
ROBUST STORM UPDRAFTS IN THE PRESENCE OF INCREASINGLY STRONG SHEAR
AND LARGER SCALE DYNAMICS.
INITIALLY QUASI-DISCRETE CELLS/SUPERCELLS WILL BECOME INCREASINGLY
FOCUSED AND TAKE ON LINEAR CHARACTERISTICS AS COLD FRONT BECOMES
BETTER DEFINED EAST OF THE HIGHER TERRAIN LATER TODAY. A FEW OF
THESE STORMS COULD PRODUCE LARGE HAIL AND POSSIBLY EVEN A BRIEF/WEAK
TORNADO BEFORE ACTIVITY MERGES AND EVOLVES INTO A SEVERE SQUALL LINE
WITH WIDESPREAD DAMAGING WINDS BECOMING MORE OF A THREAT WITH TIME.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM
MOTION VECTOR 26035.

...CARBIN

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